The present invention is related to motor drives, and in particular to motor drives employed with respect to permanent magnet synchronous motors.
Motor drives control the operation of a motor by controlling the supply of power to the motor. In particular, motor drives oftentimes include a pulse-width modulation (PWM) inverter comprised of a plurality of solid-state switching devices that are selectively turned On and Off to generate the desired alternating current (AC) waveform for supply to the motor.
A drawback of motor drives employing a PWM inverter is the creation of current harmonics on the output of the motor drive that can result in negative torque components being provided to the motor, thereby decreasing performance of the motor. The creation of current harmonics on the output of the motor drive is attributable to the dead-time of gate drives within the PWM inverter, such dead-time being added to prevent the short circuit of inverter legs, to turn On/Off times of the solid-state switching devices employed by the PWM inverter, and/or to On-voltages associated with the solid-state switching devices and diodes.
To minimize the presence of these harmonics, prior art controllers have relied on increasing the bandwidth of the current loop used to regulate the output current of the inverter. However, this solution makes the system vulnerable to noise and instability, which may amplify system resonances.